This proposal aims to elucidate the role of adenovirus (Ad) capsid fiber protein to stimulate the immune system and to deliver antigens for genetic vaccination. Incorporation of antigens into the Ad capsid is a novel and promising strategy to capitalize on the immunogenic properties of Ad and a way to circumvent preexisting anti-Ad immunity. Preliminary studies show that the most promising site for the integration of an epitope into the Ad capsid is the fiber protein. The overall hypothesis is that incorporation of epitopes in the optimal location of the Ad fiber protein can evoke potent protective anti-epitope immunity even in the presence of anti-Ad immunity. Little is known about the effect of fiber modifications on antigen presentation and anti-Ad immunity. Little is known about the effect of fiber modifications on antigen presentation and anti-Ad immunity. The knowledge gained from the proposed studies will not only be useful in the development of Ad-based vaccines, but also to identify mechanisms of the role the Ad fiber in the immunogenicity of Ad. Two specific aims will test the overall hypothesis: Aim 1 will evaluate the hypothesis that the location of a model epitope within the Ad fiber protein will influence interaction with target cells, antigen presentation and anti-epitope immune responses. Aim 2 will evaluate the hypothesis that epitopes derived from a membrane-bound and secreted antigen of two bacterial pathogens incorporated into an optimal location of the Ad fiber protein can induce protective immunity in the presence of pre-existing anti-Ad immunity. Epitopes from the Pseudomonas aeruginosa outer membrane protein F and the Bacillus anthracis protective antigen will be inserted in the optimal position of the Ad fiber, and evaluated in their potential to elicit cellular, humoral and protective anti-epitope immune responses. New methods for vaccines, as the one proposed here, will be relevant for the public health. They can aid in the development of vaccines for infections against which no or no good vaccines are available. Successful vaccines have had a profound impact on the prevention of infectious diseases over the last century.